The present invention relates to an improved liquid level controller. Frequently, process intensive industries utilize process valves, which are operated by means of a pneumatic or electrical control signal, for the control of process fluids. The pneumatic control for such valves typically includes a pilot valve, whose function is to send an output signal pressure to the pneumatic controller, which either opens or closes the process valve. In the typical prior art system, the control of liquid levels in vessels has long been accomplished through use of a float whose motion or buoyancy force is transmitted to a pneumatic or electric controller which is connected to a process valve for opening and closing flow of liquid from the vessel.
In a typical operating environment, pneumatic pressure supplied to the pilot valve is used to facilitate operational control of process valves. When the liquid level in the vessel is within the desired limit, the pneumatic pressure is withheld from a discharge port, which is used to signal activation or deactivation of a process valve. As liquid within a vessel rises or falls sufficiently to change the position of the float, the pilot valve is activated to permit transfer of the pneumatic pressure through the discharge port to control operation of a process valve. For example, selectively activating a discharge valve or inlet valve to raise or lower fluid in a vessel results from activation of the pilot valve.
Many of the prior art devices were difficult to reconfigure from a direct operating mode (rising level increases pilot valve output), to an indirect operating mode (falling level increases pilot valve output) and vice versa, often leading to an inventorying of both operational mode devices, while other prior art devices necessitate a positional change in components of the device used to transmit the buoyancy force of the float to the pilot valve.
Accordingly, as market pressures continue to demand liquid level controllers that provide lower cost, greater reliability, and improved ease of use, challenges remain and a need persists for improvements in methods and apparatuses for use in fluid level monitoring and control devices.